I used the iPaq and exbal with great confidence. The software is very pleasing to used. If I missed it was the "wind's" fault.
Due to the age of the iPaq and seemingly short battery life, especially in cold weather I switched to the iPod touch and Ballistic FTE. FTE uses the JBM algorithms and is well respected.
The feature of this combo that does away with another LRH piece of gear is the automatic shot angle compensation. Pretty nerdy kewl!
As I usually shot from a hide there is plenty of time to determine shooting angles. With the fore end bottom parallel with the bore, hold the iPod against the fore end and watch the numbers change.